The problem of cutting down resonance in induction sleeves, in particular on motor vehicles, has become more important as the overall noise of the vehicle has decreased owing to continuous improvements. Therefore, all noises that could not be heard before because covered by other noises, at present have become unpleasant and therefore have to be reduced.
One of the systems that are known and utilised in the state of the art is that of manufacturing sleeves having honeycomb-like textile inserts fitted on the walls and coupled to plastic anticollapsing structures.
The aforesaid technique is rather complex and does not always give satisfactory results. Moreover, it has a considerably high cost.